The true key to a successful, continuous game is giving people reasons to come back. Many companies rely on the many lessons granted by psychology discussion about addiction, reward, and pleasure. That is an entire career path on its own, but it's possible to create a great experience by catering to a few basics. A fun game, a community that cares about goals, and things to do other than going for a single "win" goal are just a few elements. Here are a few planning points to consider as you work on ideas for a gaming app:

Encouraging In-Game Economies

Many games have auction houses or some sort of player-owned shop system, allowing items found or made in-game to be sold. Supply and demand is the name of the game, just like in real life, but the way that goods are traded is up to you--the developer--and the players.

The easiest way for most developers to create a game economy is to set a currency. It's a simple, time-tested way to set a base value for everything else to be priced. Whether it's gold, zenny, zeni, or zeny credits, or one of many fantasy currencies, this will allow players to buy things from both Non-Player Characters (NPC) run by the game or from other players.

Trading specific items is a possibility but depends on a gaming community that is willing to go out and get things.

If you haven't played online games in a while, here's an opinion: a lot of gamers are lazy. They want to fight the cool enemies, get stronger, and work for the biggest goals. This doesn't mean that there aren't players who want to hunt specific items for their own collections or to sell to people in need. It's just not a big enough mindset to create a game community from scratch.

An item trading economy without currency requires players to find an exact thing to give to someone who has what they want. You need to already know that players are interested, will stay interested, and have already played this way for years.

Start out with currency, and consider implementing such trading experiments later. For the most part, players want to just fight enemies for money generated by the game, buy what they need, and sell items when they're lucky enough to get something. The item hunters and self-making quest players can still enjoy the game.

Be Careful With In-App Stores

You have to be a bold developer to charge money for a mobile app, let alone a subscription. How can you and your team get paid while getting exposure and creating a community?

Well, advertisements first. Always advertisements.

After that, in-game shops can allow players to either buy power or buy appearances. Unfortunately, some in-game shops are disliked by the gaming community at large and can shun a sizable portion of your player base. Big companies can get away with tempting an existing population, but you should offer a tastier gaming fruit.

Avoid selling game-breaking products that allow players to defeat others or reach the endgame quickly. Many players will simply stop playing after "winning" in their minds, and players who earn their way in-game will be turned off. 

Opt for the most basic items that players don't need after getting halfway through the game, or offer chances to get a small advantage that can still fail. Contact an app design services professional to discuss ways to not only code a robust economy but figure out how to test the community and make changes consistently.